Asexual reproduction
Plants exhibit a variety of reproductive strategies,
and the specific method a plant uses for
reproduction is often influenced by evolutionary
adaptations and ecological factors. Different plant
species have evolved to use specific structures or
organs for reproduction based on their survival
needs and environmental conditions.
Different plants have evolved various strategies for
asexual reproduction, and the choice of vegetative
parts involved in reproduction is often influenced
by the plant's anatomy, physiology, and
environmental conditions.
Embryology
• It is the branch of science that deals with the structure of embryo
including sporogenesis, gametogenesis, pollination, fertilization and
endosperm development.
Asexual reproduction
• New individuals are formed from specialized or non-specialized parts
of single parent without meiosis cell division, formation of gamate
and their fusion.
• Offspring is genetically similar to the single parental organism.
• There are three types of asexual reproduction.
A. agamospermy B. spore formation C. Vegetative propagation
A. agamospermy (plant apomixis)
1. adventive embryony- formation of embryo directly from the diploid
cells of nucellus or integuments of ovule without formation and fusion
of gamete is called adventive embryony eg. Citrus, Opuntia sp.
1. Adventive embryony
• The formation of embryo directly from the diploid ells of nucellus of
integuments of ovule without formation and fusion of gametes is
called adventive embryony.
2. Diplospory
• In this case, archesperial cell differentiates and forms megaspore
mother cell. But megasore mogher cell directly gives rise to embryo
sac without meiosis. It may produce two types of embryo.
Vegetative propagation
• It is an asexual method of plant reproduction that occurs in its leaves,
roots and stem. This can occur through fragmentation and
regeneration of specific vegetative parts of plants.
• The vegetative parts involve in this type of reproduction are called
propagules.
• It is of two types’
1. natural vegetative propagation
2. artificial vegetative propagation.
Vegetative propagation through
roots.
• Modified tuberous roots in sweet
potato.
• The buds present in the root grow
into leafy shoots called slips above
ground and advantitious roots at
their bases.
• Each slips give rise to new plants.
• Dahlia sp.
Vegetative reproduction by roots.
Vegetatve propagation through
stem.
• Underground stem-
• Rhizome- it is peennial underground
modified stem which is thick, fleshy
due to the presence of storage foods.
• Each rhizome contains scale leaves
and axillary buds in the nodes. Axillary
roots arise from the lower side of
Bulb
• A bulb has a very short condensed disc shaped
stem present at the base of fleshy storage scale
leaves.
• It bears a number of apical and axillary buds.
Tunicated bulb in onion.
Corm of Colocasia sp.
Sucker
Sucker
• It is a special non-green underground
stem branch which grows form the
base of aerial shoot called crown.
• It bears scale leaves and axillary buds
on its nodes. It grows horizontally in
the soil and then bends out to form a
new crown. The process is repeated.
The aerial shoots are also produced by
axillary buds present on the sucker
e.g. Chrysanthemum, mint etc.
Sub-aerial
Sub aerial stem
•.
Sub-aerial
Vegetative propagation by Aerial
stem
• Opuntia is flattened green leafy like stem. Each
phylloclade produces number of buds. When
these buds detached from phylloclade, they
give rise to new plant body.
Vegetative propagation through
leaves
Begonia.
Vegetative propagation through
bulbils.
• Bulbils arise in the axils of leaves in lily and
yam.
• Bulbils are found in the inflorescence and
replace flowers in garlic and agave.
• It is found in adjacent fruits in pineapple.
Bulbils
Bulbill of Pineapple
Turions
• They are special type of fleshy buds
developed in aquatic plants.
• Eg. Utriculara sp., Potamogeton sp.
Artificial Vegetative PropagationIn this, a part of a
plant, specifically a stem or leaf is cut and planted
in the soil. These cuttings are sometimes treated
with hormones to induce root development. The
new plant is formed from the adventitious roots
developing from the cutting.
.
• Cutting is applicable
in rose, Geranium,
Euphorbia, Duranta,
sugarcane, grapes,
Baugainvellea etc.
Cutting :
•.
cutting
.
Types of layering
soil layering
• Simple layering
• Eg. Grape vine, jasmine, straw
berry, cherry, Ipomia
• Tip layering eg. Blackberry,raspberry.
• Serpentine layering
eg. Clematis
• Mound layring eg. Gooseberry
• Trench layering eg. Walnut
Air layering
(GOOTY)
• Applicable for that plant which
has hard branches that lie far
away from the soil.
• A ring of bark is removed from
the base of aerial branch and it
is covered by moist grafting clay.
• (2 part clay, 1 part cow dung,
low concentration of auxin,
some fine cut hay, mosses and
herbs)
Grafting
•.
Examples.
• Development of water melon in the root of stock of pumping is an
example of approach grafting.
• Bud grafting is done in rose , peach, apple etc.
• Tongue grafting-
Asexual Reproduction
• Apomixis- The methods of reproduction which do not involve meiosis
and fertilization are known as apomixis.
• The offsprings are same as that of the parent in all aspects.
• There is an involvement of mitosis cell division only.
Agamospermy
• It is a type in which seeds and embryo are formed without meiotic
division of gametes and their fusion.
• Many flowering plants and ferns may develop by agamospermy.
• 1- Adventive embryony- the formation of embryo directly from the
diploid cells of nucellus or integuments of ovule without formation
and fusion of gametes is called adventive embryony. eg. Citrus,
Opuntia
• Diplospory- in this case, archesporial cell differentiates and forms
megaspore mother cell. This megaspore mother cell directly gives rise
to embryo sac without meiosis.
Diploid Parthenogenesis
• Embryo develops from unfertilized diploid egg cell.
ii. Diploid apogamy
• Embryo develops from diploid cell of embryo sac except egg cell
without fertilization.
Apospory
• It is a process of formation of complete embryo sac from sporophytic
cells without meiosis so, that the gametophyte remains diploid.
• 1- Somatic apospory- embryo sac is formed from somatic cells.
• 2- Generative apospory- embryo sac is formed from archesporial cells
without meiosis.
B. Spore formation
• Spores formed in this type of reproduction are due to mitosis eg.
Zoospores, aplanospores, conidia, akinetes, hypnospores etc.
• This type of asexual reproduction occurs only in algae and fungi.
